Musical synthesis envelope control techniques

Abstract

The disclosure describes improved apparatus for synthesizing an audible note from its volume, attack-decay envelope and waveshape characteristics. By employing multiplying analog-to-digital converters, the characteristics can be rapidly generated and combined in real time, thereby enabling the use of the synthesis in performing instruments.

What is claimed is: 
     
       1. A method of synthesizing an audible note comprising the steps of: generating a time-spaced series of digital amplitude numbers representing the average amplitude of the note at discrete instants in time, said step of generating a time-spaced series of digital amplitude numbers comprising the separate steps of generating a time-spaced series of digital volume numbers representing the average volume component of the note amplitude and generating a time-spaced series of digital envelope numbers representing the attack or decay envelope component of the note amplitude;   generating a time-spaced series of digital wave numbers representing the waveshape and fundamental frequency characteristics of the note at discrete instants in time;   converting the series of digital amplitude numbers into a corresponding analog amplitude signal;   multiplying the value of the analog amplitude signal and the digital wave numbers together to generate an analog tone signal; and   converting the analog tone signal into the audible note, whereby the composite and complex characteristics of the note can be rapidly generated in real time.   
     
     
       2. A method, as claimed in claim 1, wherein: the step of converting the series of digital amplitude numbers comprises the steps of generating a reference analog signal, multiplying the value of the reference analog signal and the digital volume numbers together to form a volume analog signal, multiplying the values of the volume analog signal and the digital envelope numbers together to form the analog amplitude signal, and multiplying the values of the analog amplitude signal and the digital wave numbers together to form the analog tone signal.   
     
     
       3. Electronic apparatus for synthesizing an analog tone signal suitable for conversion to an audible note comprising: amplitude generator means for generating a time-spaced series of digital amplitude numbers representing the amplitude of the note at discrete instants in time, said amplitude generator means comprising separate generator means for generating a separate and distinct time-spaced series of digital volume numbers representing the volume component of the note amplitude at discrete instants in time and separate and distinct envelope generator means for generating a separate and distinct time-spaced series of digital envelope numbers representing the attack or decay envelope component of the note amplitude at discrete instants in time;   waveshape generator means for generating a time-spaced series of digital wave numbers representing the waveshape and fundamental frequency characteristics of the note at discrete instants in time; and   conversion means for converting and combining the series of digital numbers representing respectively the volume of the note, the attack or decay envelope of the note, and the waveshape and fundamental frequency of the note into an analog tone signal, whereby the composite complex characteristics of a note can be rapidly generated and combined into a tone signal in real time, said conversion means comprising first converter means for multiplying the value of a reference analog signal and the digital volume numbers together to form a volume analog signal, second converter means for multiplying the values of the volume analog signal and the digital envelope numbers together to form the analog amplitude signal, and third converter means for multiplying the values of the analog amplitude signal and the digital wave numbers together to form the analog tone signal.   
     
     
       4. Apparatus, as claimed in claim 1, wherein the first converter means, the second converter means and the third converter means each comprises a multiplying digital-to-analog converter and digital latch means connected as input respectively to each said multiplying digital-to-analog converter. 
     
     
       5. Electronic apparatus for simultaneously synthesizing a first tone signal and a second tone signal suitable for conversion to a first audible note and a second audible note comprising: first amplitude generator means for generating a time-spaced series of first digital amplitude numbers representing the average amplitude of the first note at discrete instants in time, said first amplitude generator means comprising volume generator means for generating a time-spaced series of first digital volume numbers representing the average volume component of the first note amplitude at discrete instants in time and envelope generator means for generating a time-spaced series of first envelope numbers representing the attack or decay envelope component of the first note amplitude at discrete instants in time;   second amplitude generator means for generating a time-spaced series of second digital amplitude numbers representing the average amplitude of the second note at discrete instants in time, said second amplitude generator means comprising volume generator means for generating a time-spaced series of second digital volume numbers representing the average volume component of the second note amplitude at discrete instants in time and envelope generator means for generating a time-spaced series of second digital envelope numbers representing the attack or decay envelope component of the second note amplitude at discrete instants in time;   first waveshape generator means for generating a time-spaced series of first digital wave numbers representing the waveshape and fundamental frequency characteristics of the first note at discrete instants in time;   second waveshape generator means for generating a time-spaced series of second digital wave numbers representing the waveshape and fundamental frequency characteristics of the second note at discrete instants in time;   first conversion means for converting the series of first digital amplitude numbers into a corresponding first analog amplitude signal and for multiplying the value of the first analog amplitude signal and the first digital wave numbers together to form a first analog tone signal; and   second conversion means for converting the series of second digital amplitude numbers into a corresponding second analog amplitude signal and for multiplying the value of the second analog amplitude signal and the second digital wave numbers together to form a second analog tone signal, whereby independent control can be maintained over the amplitude and waveshape characteristics of the first and second tone signals or any resulting audible notes.   
     
     
       6. Apparatus, as claimed in claim 4, wherein: the first conversion means comprises first converter means for multiplying the value of a reference analog signal and the first digital volume numbers together to form a first volume analog signal, second converter means for multiplying the values of the first volume analog signal and the first digital envelope numbers together to form the first analog amplitude signal, and third converter means for multiplying the values of the first analog amplitude signal and the first digital wave numbers together to form the first analog tone signal.   
     
     
       7. Apparatus, as claimed in claim 6, wherein the first, second and third converter means each comprises a multiplying digital-to-analog converter and latch means connected as input to each said multiplying digital-to-analog converter. 
     
     
       8. An electronic musical instrument for synthesizing an audible note comprising: performer controllable key means for selecting the note to be synthesized;   waveshape generator means for generating a time-spaced series of digital wave numbers representing the waveshape and fundamental frequency characteristics of the note at discrete instants in time;   performer controllable volume means for generating a time-spaced series of digital volume numbers representing the average volume of the note at discrete instants in time;   envelope generator means for generating a time-spaced series of digital envelope numbers representing the attack or decay envelope of the note at discrete instants in time;   first converter means for multiplying the value of a reference analog signal and the digital volume numbers together to form a volume analog signal;   second converter means for multiplying the values of the volume analog signal and the digital envelope numbers together to form the analog amplitude signal;   third converter means for multiplying the values of the analog amplitude signal and the digital wave numbers together to form an analog tone signal; and   output means for converting the analog tone signal into the audible note, whereby the composite complex characteristics of the note can be rapidly generated and combined in real time.   
     
     
       9. Apparatus, as claimed in claim 8, wherein the first, second and third converter means each comprises a multiplying digital-to-analog converter and latch means connected as input to each said multiplying digital-to-analog converter. 
     
     
       10. An electronic musical instrument for simultaneously synthesizing a first audible note and a second audible note comprising: first performer controllable key means for selecting the first note for synthesizing;   first performer controllable volume means for generating a time-spaced series of first digital volume numbers representing the average volume component of the first note amplitude at discrete instants in time;   first envelope generator means for generating a time-spaced series of first digital envelope numbers representing the attack or decay envelope of the first note at discrete instants in time;   second performer controllable volume means for generating a time-spaced series of second digital volume numbers representing the average volume of the second note at discrete instants in time;   second envelope generator means for generating a time-spaced series of second digital envelope numbers representing the attack or decay envelope of the second note at discrete instants in time;   first waveshape generator means for generating a time-spaced series of first digital wave numbers representing the waveshape and fundamental frequency characteristics of the first note at discrete instants in time;   second waveshape generator means for generating a time-spaced series of second digital wave numbers representing the waveshape and fundamental frequency characteristics of the second note at discrete instants in time;   first converter means for multiplying the value of a reference analog signal and the first digital volume numbers together to form a first volume analog signal;   second converter means for multiplying the values of the first volume analog signal and the first digital envelope numbers together to form a first analog amplitude signal;   third converter means for multiplying the values of the first analog amplitude signal and the first digital wave numbers together to form the first analog tone signal;   fourth converter means for multiplying the value of a reference analog signal and the second digital volume numbers together to form a second volume analog signal;   fifth converter means for multiplying the values of the second volume analog signal and the second digital envelope numbers together to form a second analog amplitude signal;   sixth converter means for multiplying the values of the second analog amplitude signal and the second digital wave numbers together to form the second analog tone signal; and   output means for simultaneously converting the first and second tone signals into the first and second audible notes, whereby independent control can be maintained over the amplitude and waveshape characteristics of the first and second notes.   
     
     
       11. Apparatus, as claimed in claim 10, wherein the first, second, third, fourth, fifth and sixth converter means each comprises a multiplying digital-to-analog converter and latch means connected as input to each said multiplying digital-to-analog converter. 
     
     
       12. Electronic apparatus for synthesizing an analog tone signal suitable for conversion to an audible note comprising, in combination: volume generator means for generating a time-spaced discrete series of digital volume numbers representing the volume component of the note amplitude at discrete instants in time; envelope generator means for generating a time-spaced discrete series of digital envelope numbers representing the attack and decay envelope components of the note amplitude at discrete instants in time; wave generator means for generating a time-spaced discrete series of digital wave numbers representing the waveshape and fundamental frequency components of the note at discrete instants in time; and means operable to convert and combine the digital numbers representative of the volume of the note, the attack and decay envelope of the note and the waveshape and fundamental frequency of the note into a tone signal in real time, said means operable to convert and combine comprising the combination of digital latch means and multiplying digital-to-analog converter means that receives the digital numbers representative of the volume of the note, the attack and decay envelope of the note and the waveshape and fundamental frequency of the note and converts and combines said digital numbers to provide said tone signal in real time.